1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device and a method of driving the same.
2. Discussion of the Related Art
Until recently, display devices have typically used cathode-ray tubes (CRTs). Presently, many efforts and studies are being made to develop various types of flat panel displays, such as liquid crystal display (LCD) devices, plasma display panels (PDPs), field emission displays, and electro-luminescence displays (ELDs), as a substitute for CRTs. Of these flat panel displays, LCD devices have many advantages, such as high resolution, light weight, thin profile, compact size, and low voltage power supply requirements.
In general, an LCD device includes two substrates that are spaced apart and face each other with a liquid crystal material interposed between the two substrates. The two substrates include electrodes that face each other such that a voltage applied between the electrodes induces an electric field across the liquid crystal material. Alignment of the liquid crystal molecules in the liquid crystal material changes in accordance with the intensity of the induced electric field into the direction of the induced electric field, thereby changing the light transmissivity of the LCD device. Thus, the LCD device displays images by varying the intensity of the induced electric field.
The LCD device uses a backlight to supply light to a liquid crystal panel. A cold cathode fluorescent lamp (CCFL) and an external electrode fluorescent lamp (EEFL) are widely used as the backlight. Recently, a light emitting diode (LED) has been used as the backlight.
FIG. 1 is a schematic view illustrating a multi-channel type LED backlight and a multi-channel type driving circuit according to the related art.
Referring to FIG. 1, the backlight 40 includes a plurality of channels CH1 to CHn, and a plurality of LEDs are arranged along each of the channels CH1 to CHn. The channels CH1 to CHn are connected to the multi-channel type driving circuit 45 which separately operates the channels CH1 to CHn.
The multi-channel type driving circuit 45 separately outputs a plurality of driving voltages through a plurality of output terminals OUT1 to OUTn into the plurality of channels CH1 to CHn, respectively, and separately receives feedbacks of the plurality of channels CH1 to CHn through a plurality of feedback terminals FB1 to FBn, respectively, to check the status of each channel. Accordingly, the driving circuit 45 makes a desired current flow on the corresponding channel. Further, when at least one LED has a defect such as open-circuit defect or short-circuit defect, the driving circuit 45 performs a protection operation for the channel having the defective LED.
However, the multi-channel type driving circuit 45 is expensive, and thus production costs increase. To reduce production costs, a relatively cheap single channel type driving circuit is used for the multi-channel type LED backlight.
FIG. 2 is a schematic view illustrating a multi-channel type LED backlight and a single-channel type driving circuit according to the related art.
Referring to FIG. 2, the single-channel type driving circuit 46 includes one output terminal OUT and one feedback terminal FB. A plurality of channels CH1 to CHn are connected in common to the output terminal OUT and the feedback terminal FB thus controlled in common by the single-channel type driving circuit 46.
However, since the channels CH1 to CHn are connected in common to the feedback terminal FB, it is difficult to check the status of each channel. In other words, even though at least one channel is defective, a feedback detected through the feedback terminal FB is substantially the same as a feedback when all channels are in normal status. Accordingly, the backlight 40 is recognized as if it had a normal status, and thus the defective channel cannot be found and a protection operation for the backlight 40 cannot be performed.
For example, when one of the channels CH1 to CHn has an open-circuit defect, other channels in normal status have an overcurrent, and thus the LEDs therein may be damaged. Further, when one of the channels CH1 to CHn has a short-circuit defect, the defective channel has an overcurrent, and thus the LEDs therein may be damaged.
As such, when the single-channel type driving circuit is used for the multi-channel type LED backlight, the defective channel cannot be found. Accordingly, a protection operation for the LED backlight cannot be performed.